This invention relates to a display apparatus, wherein an electrooptic layer is driven by the use of plasma to select pixels, and to a method of driving the display apparatus.
In recent years, various display apparatuses are available. Among them are display apparatuses having a PDP (Plasma Display Panel), display apparatuses having a TFT (Thin-Film Transistor) liquid crystal display, and display apparatuses having a plasma-addressing liquid crystal display (hereinafter called PALC display). The PALC display apparatus, in particular, attracts attention, because it can provide a large screen.
FIG. 1 shows the basic structure of the PALC display apparatus.
As shown in FIG. 1, the PALC display apparatus comprises a liquid crystal layer 101 made of electrooptic material, plasma chambers 102, and a thin dielectric sheet 103 that is made of glass or the like. The layer 101 opposes the chambers 102, with the sheet 103 interposed between it and the chambers 102.
The plasma chambers 102 are defined by a plurality of parallel grooves 105 made in a surface of a glass substrate 104. The chambers 102 are filled with gas that can be ionized. A pair of electrodes 106 and 107, which extend parallel to each other, is provided in each of the grooves 105. The electrodes 106 and 107 of each pair are an anode A and a cathode K, which ionize the gas in the plasma chamber 102, thereby generating discharge plasma.
The liquid crystal layer 101 is held between the dielectric sheet 103 and a transparent substrate 108. Transparent electrodes 109 are provided on that surface of the transparent substrate 101 which opposes the liquid crystal layer 101. The transparent electrodes 109 extend at right angles to the grooves 105 that define the plasma chambers 102. The intersections of the plasma chambers 102 and the transparent electrodes 109 correspond to pixels.
In this display apparatus, the plasma chambers, in which plasma discharge is effected, are sequentially scanned, and a signal voltage is applied to the transparent electrodes 109 contacting the liquid crystal layer 101 as the plasma chambers are thus scanned. As a result, the pixels hold the signal voltage, thereby driving the liquid crystal layer 101.
Each groove 105, or each plasma chamber 102, corresponds to one scanning line. The chamber 102 is divided into discharge regions, which define unit-scanning spaces.
FIG. 2 is a schematic representation of the PALC display apparatus, illustrating the arrangement of the transparent electrodes 109, anode electrodes A and cathode electrodes K.
The transparent electrodes 109 are connected to a transparent electrode driving section, which comprises a data driver circuit 110 and an output amplifiers 111. The analog voltage output from each amplifier 111 is supplied as a liquid-crystal drive signal.
The cathode electrodes K1 to Kn are connected to a cathode driving section, which comprises a data strobe circuit 112 and output amplifiers 113. More specifically, the cathode electrodes K1 to Kn are connected to the output amplifiers 113, respectively. Each output amplifier 113 outputs a pulse voltage, which is applied, as a data strobe signal, to the corresponding cathode electrode. A reference voltage (i.e., ground voltage) is applied to all anode electrodes A1 to An.
The anode electrodes A and the cathode electrodes K are connected as is illustrated in FIG. 3.
The display apparatus has a scanning control circuit 114, which is connected to the data driver circuit 110 and data strobe circuit 112. The scanning control circuit 114 serves to display an image on the entire screen of the display apparatus. The circuit 114 is designed to adjust the functions of the data driver circuit 110 and data strobe circuit 112 in order to designate addresses of lines, one after another, for all columns of pixels in the liquid crystal layer 101.
In the display apparatus, the liquid crystal layer 101 operates as a capacitor for sampling the analog voltage applied to the transparent electrodes 109. The discharge plasma generated in the plasma chambers 102 operates as a sampling switch. As the layer 101 and the plasma so operate, the display apparatus displays images.
In the PALC display apparatus, the plasma channels may be sequentially scanned, from the uppermost one to the lowermost one, and the liquid-crystal drive signal may be supplied to the liquid crystal layer 102 (more specifically, to the transparent electrodes 109) as the plasma channels are so scanned. In this case, plasma discharge takes place between the anode electrodes A, on the one hand, and the cathode electrodes K, on the other, as is illustrated in FIG. 4. FIG. 5 shows the waveform of the liquid-crystal drive signal supplied to the transparent electrodes 109 in this case. The numbers identifying the anode electrodes A and cathode electrodes K in FIG. 4 indicate the order in which the anode electrodes and the cathode electrodes are arranged in the same column. Each letter x in FIG. 4 shows the position where plasma discharge occurs between one cathode electrode K and the corresponding anode electrode A. The numbers added to the letters x represents the order in which the plasma discharge takes place.
For instance, plasma discharge occurs at position x1 between the cathode electrode K1 and the anode electrode A1, and at position x2 between the cathode electrode K2 and the anode electrode A2. Similarly, plasma discharge takes place at position xm between the cathode electrode Km and the anode electrode Am, at position xm+1 between the cathode electrode Km+1 and the anode electrode Am+1, and a position xm+2 between the cathode electrode Km+2 and the anode electrode Am+2.
In FIG. 5, LCm is the waveform of the liquid-crystal drive signal that is supplied to the transparent electrodes 109 arranged in the horizontal direction. L1 to L9 in FIG. 5 indicate the times at which horizontal scanning is performed. In the case illustrated in FIGS. 4 and 5, the anode electrodes A are always at a constant potential (0 V), while the potentials of, for example, the cathode electrodes Km, Km+1 and Km+2 are switched between 0 V and xe2x88x92400 V, thereby to cause discharge in these plasma channels.
The manufacturing costs of the drive circuit incorporated in the PALC display apparatus is high. It is therefore difficult for the PALC display apparatus to avail commercially. The manufacturing costs of the drive circuit is high for two reasons. Primarily, the drive circuit has many output terminals. Secondly, the drive voltages output from these output terminals are high. In a PALC display apparatus of VAG (Video Graphics Array) standard, which has image resolution of 640xc3x97480 pixels, the drive circuit needs to have 480 discharge output terminals to achieve the switching of the cathode electrodes. In addition, the drive voltage output from each output terminal may amount to 400 V in some cases.
The present invention has been made in view of the foregoing. The object of the invention is to provide a PALC display apparatus that can be manufacture at low cost and display images of high quality, and to provide a method of driving the PALC display apparatus.
According to the invention, there is provided a display apparatus which comprises: a first electrode layer having a plurality of first electrodes extending substantially parallel to one another; a second electrode layer having a plurality of second electrodes extending substantially parallel to one another, each composed of at least one pair of discharge electrodes, and arranged with the second electrodes opposing the first electrodes and extending to the first electrodes; and electrooptic layer provided between the first electrode layer and the second electrode layer and substantially contacting the first electrode layer, to be driven by said at least one pair of discharge electrodes; and a discharge region provided between the first electrode layer and the second electrode layer, filled with gas that can be ionized, and having barrier ribs extending substantially parallel to the second electrodes. The apparatus further comprises: connection means dividing the second electrodes into groups and connecting the discharge electrodes included in each group to one another; and voltage-applying means for applying two voltages of the opposite polarities to selected two of the groups, respectively.
According to the invention, there is provided a method of driving a display apparatus of this type.
In the display apparatus and the method of driving the apparatus, both according to the present invention, a voltage is applied to the discharge electrodes at the same position, with a time lag of at least one scanning period, thereby to perform sequential line scanning.